This invention relates to a voltage variable delay circuit and, more particularly, to a programmable delay circuit which comprises complementary inverter elements that are responsive to a variable voltage that controls the amount of delay provided by the circuit to an applied signal.
Delay circuits are well known for establishing a desired time delay which is imparted to an input signal and one such circuit is described in U.S. Pat. No. 4,482,826 of Ems et al. This patent of Ems et al. discloses a circuit in which the imparted delay is controlled by adjusting its operating voltage. The circuitry uses a complex analog device, such as an operational amplifier, for controlling the time delay. The fabrication techniques for providing complex analog devices on an otherwise digital integrated circuit increases the manufacturing expense. Thus, it is desirable that a variable delay circuit be provided that does not use complex analog circuits requiring expensive forming techniques.
Accordingly, it is an object of the present invention to provide an adjustable delay circuit in which the control of the delay is accomplished without the use of complex analog devices formed by expensive techniques.
It is a further object to provide a very accurately controlled delay for time-delay circuit applications.
It is a further object to provide an accurately controlled delay circuit for oscillator circuit applications.
It is a further object of the present invention to provide for means for accurately controlling and adjusting the delay imparted to a signal applied to either the delay circuit or the frequency generated by the oscillator.
Various objects, advantages and features of the present invention will become readily apparent from the ensuing detailed description, and the novel features will be particularly pointed out in the appending claims.